(a) Field of the Invention
This invention relates to a vehicle door placed on each side of a vehicle such, for example, as a passenger car.
(b) Description of the Related Art
There is a type of conventional vehicle door that has a sash formed on top of a door body to surround a window glass as disclosed, for example, in Patent Document 1 (Japanese Unexamined Patent Publication No. S58-209617) and Patent Document 2 (Japanese Unexamined Patent Publication No. H08-142677). The sash of this type is composed of a rear side part extending upward from a rear-side upper part of the door body along the rear edge of the window glass, and a top side part connected to the upper end of the rear side part and extending frontward along the top edge of the window glass.
The sash in Patent Document 1 is constructed by joining an outer panel to an inner panel. The inner panel is roll-formed to have a closed cross section. On the other hand, the sash in Patent Document 2 is composed of a single, roll-formed plate.
During a high-speed run of a vehicle, a large pressure difference is caused between the vehicle interior and the outside so that a force toward the outside of the vehicle acts on the window glass. As a result, the sash is acted on by an external force to tend to shift its upper end toward the outside of the vehicle with respect to its lower end located at the boundary with the door body. In order to withstand this external force, it is necessary to enhance the rigidity of the sash. If, however, a sash is formed in a closed cross section only by roll forming like the above Patent Documents 1 and 2, it is difficult to roll-form the sash to alter its cross-sectional shape along its length. Therefore, the rigidity of the sash cannot sufficiently be enhanced.
The present invention has been made in view of the above point and its object is to ensure the rigidity of the sash by making it possible to flexibly design the shape of the rear side part of the sash.